Work begins on the metering block, which
has been placed in a spotless aluminum
tray. The other Holley carb shown here
(foreground) was also scheduled for
rebuilding and tuning that day.

New jet sizes are part of the carburetor
hop-up. Passageways going to the power
valve are also enlarged. The size of
the replacement power valve is part
of the secret recipe.

All the care in the world doesn't mean
anything if the reassembled carburetor
leaks. Even on a relatively new carb
like this one, the gasket material needs
a little gentle persuasion with a fine-wire
brush to create a clean surface for
the new gaskets. Similar modifications
were performed on the forward metering
block; the carb was then reassembled
on the engine.

RPM

HP

TQ

2,800

152.30

285.69

2,900

163.15

295.48

3,000

170.56

298.60

3,100

181.43

307.38

3,200

189.66

311.28

3,300

193.06

317.81

3,400

205.74

317.81

3,500

212.66

319.12

3,600

220.02

320.99

3,700

227.33

322.69

3,800

232.87

321.86

3,900

237.50

319.85

4,000

243.43

319.62

4,100

245.84

315.57

4,200

250.25

312.93

4,300

255.85

312.50

4,400

259.06

309.23

4,500

259.18

302.50

4,600

264.33

301.81

4,700

263.62

300.18

4,800

275.27

301.20

4,900

277.63

297.58

5,000

283.13

297.41

5,100

287.16

295.72

5,200

289.48

292.38

Spaccarotella does a final walkaround
and safety check before firing up the
Mustang. Not shown in the photo is an
even larger fan to ensure adequate engine
cooling.

After two pulls, it is clear that a
few more small adjustments are needed.
The engine stumbled when the throttle
was nailed, so Spaccarotella increased
the volume of the primary accelerator
pump shot as well as the volume for
the rear pump.

As a final step before testing, Spaccarotella
enlarges the air-bleed passageways by
an unknown amount. The exact balance
of the modifications he does is the
secret to success. When Superior Automotive
rebuilds your Holley carb, you get every
trick in its proven book. Once the Mustang
was run on the rollers, it didn't take
long to notice a worthwhile gain.